CN101123802B - Method and device for selecting access point in wireless LAN - Google Patents
Method and device for selecting access point in wireless LAN Download PDFInfo
- Publication number
- CN101123802B CN101123802B CN 200610110741 CN200610110741A CN101123802B CN 101123802 B CN101123802 B CN 101123802B CN 200610110741 CN200610110741 CN 200610110741 CN 200610110741 A CN200610110741 A CN 200610110741A CN 101123802 B CN101123802 B CN 101123802B
- Authority
- CN
- China
- Prior art keywords
- channel
- access point
- wireless terminal
- time
- information
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Abstract
The invention relates to a method of selecting an access point in a wireless network including the steps of that a wireless terminal carries out channel scan on a channel k in the wireless network, receives channel information sent out from the access point and takes out the channel utility ratio uk; confirms the maximum data transmission rate vk that can be supported by the current channel according to the received channel information; counts the channel acquisition probability rk in a scanning time space and calculates a hidden terminal influence factor fk according to the channel utility ratio uk, the maximum data transmission rate vk and the channel acquisition probability rk; carries out the processes on all the channels that can be accessed by the wireless terminal repeatedly, selects an access point AP corresponding to the minimum value of f that are calculated and adds in the basic operation group that the selected access point lies in.
Description
Technical field
The present invention relates in WLAN, select the method and apparatus of access point; Particularly; Relate in association (Association) and re-associates (Reassociation) process in WLAN and select access point (AP; Access Point) method and apparatus can be estimated the influence that when inserting this AP, is brought by concealed terminal through making the busy extent of wireless terminal difference measured channel on available channel; Thereby reduce the collision of upstream packet, and improve the overall performance of WLAN.
Background technology
Continuous propelling along with standardized process; WLAN (WLAN; Wireless Local AreaNetwork) because of characteristics such as its low cost and high transfer rates, begins to be widely used in public hot spots areas such as enterprise, office, the high-speed radio access service of internet is provided.Particularly in the large-scale application of WLAN; The elementary cell of a plurality of WLANs (cell: the sub-district); The basic service set that just defines in the IEEE802.11 standard (BSS, Basic Service Set) can overlap and realize seamless covering; So just produced BSS, just the selection problem of AP.
In the standard of WLAN, using is IEEE802.11 series the most widely.IEEE802.11 series occurs with two kinds of various network versions usually.A kind of is the WLAN that does not have the self-organizing mode of WAP (AP), directly communicates between wherein all wireless terminals; Another kind is the WLAN of framework formula, and its elementary cell is the basic service set (BSS) that comprises a WAP and a plurality of wireless terminals.In framework formula WLAN, the communication of terminal room in all wireless terminals are realized netting through AP, and a plurality of BSS can constitute extended service set (ESS) to realize the expansion of coverage.
In current WLAN, owing to exist a plurality of covering overlapping areas, so each wireless terminal need carry out access point and select when getting into the coverage of WLAN, to confirm to insert which sub-district.For this reason; Wireless terminal can scan wireless channel successively and whether have available access point (AP) near detecting it when getting into the coverage of WLAN; And the AP that usually selects to have strong cohesiveness collections of letters energy indication (RSSI) is related (Association) with it, thereby adds the BSS that this AP belongs to.
Fig. 1 shows wireless terminal is selected access point in WLAN sketch map.As shown in Figure 1, access point AP1 and access point AP2 are operated in two non-overlapped channels respectively.Wireless terminal MT1 is the wireless terminal related with AP1, and wireless terminal MT2 is the wireless terminal related with AP2.When user MT3 gets into WLAN, scan available wireless channel respectively, indicate (RSSI) to decide selection to want the BSS that adds through strong cohesiveness the collections of letters energy that receives from AP1 and AP2.Defined two kinds of scan channel modes in the IEEE802.11 standard, that is, and drive sweep and active scan (as shown in Figure 2).Drive sweep is meant that wireless terminal intercepts each wireless channel successively, selects access point (shown in Fig. 2 a) through detecting beacon (Beacon) the grouping energy that sends from the periodicity of AP.Beacon packet comprises some information specific in the current area.The user can extract relevant information from the beacon packet that receives, for example, and information such as the rate set that this sub-district is supported, channel utilization.Active scan is meant wireless terminal after getting into WLAN, on each wireless channel, sends probe requests thereby grouping (Probe Request) successively.Access point AP is receiving this grouping back response response detected (Probe Response) grouping.During dividing into groups, response detected comprises in the respective cell for information about.Wireless terminal is selected access point (shown in Fig. 2 b) through detecting the energy that divides into groups from response detected.
In addition, along with the dynamic change of network, the communication conditions of wireless terminal in related BSS also can change, and when the service quality of wireless terminal can not get ensureing, need carry out re-associates to AP, and this exists the selection problem of access point equally.
Though the process that above-mentioned access point is selected simply is easy to realize that this method has only been considered the self-condition of new access node.When the service load maldistribution of two BSS, select the strongest AP of signal energy can increase the weight of the bigger BSS load of traffic density, thereby cause the decline of entire system performance.For this reason, the method that more effective AP selects has been proposed.
In the most frequently used 802.11 product, adopt the decision method of strong cohesiveness collection of letters energy indication (RSSI) to select access point usually.In other words, when a mobile node can detect plural access point, indicate the access point of selecting to have maximum RSSI according to the signal energy that receives.The problem of this method is, when the load of two sub-districts not simultaneously, a sub-district may occur and block up very much, and another sub-district is very idle, thereby cause the inequitable situation of each BSS.
Therefore, some having occurred utilizes load to select the prior art of AP.S.Misra and
A. BanerjeeThe article of delivering that is entitled as " A Novel Load Sensitive Algorithm for AP selection in4G Networks " is (referring to CODEC 2003; Calcutta; INDIA; 2003) proposed to consider the AP system of selection of load, wherein each wireless terminal selects current load minimum and be in access point on the wireless terminal moving direction.The factor of load also considered in the article (referring to VTC2004-Fall) that is entitled as " Performance of an efficient method for association admission control inpublic wireless LAN systems " that people such as Hyun-woo Lee deliver.This article disclosed through the number that in beacon and response detected are divided into groups, inserts wireless terminal in the current BSS and traffic carrying capacity (bps) select access point preferably.In addition, S.Vasudevan, K.Papagiannaki; C.Diot, the article that is entitled as " FacilitatingAccess Point Selection in IEEE 802.11 Wireless Networks " that J.Kurose and D.Towsley deliver is (referring to ACM Internet Measurement Conference; New Orleans; LA, October, 2005) proposed to utilize the difference of timestamp and target beacon delivery time (TBTT) in the beacon packet estimate can obtainable bandwidth method.But the prerequisite of this prediction is beacon packet and packet to be transmitted with same priority.Yet beacon packet is actually and has precedence over that data send, and this has just caused forecasting inaccuracy true.The article that is entitled as " Link Quality based AssociationMechanism in IEEE 802.11h compliant.Wireless LANs " that people such as T.Korakis deliver (referring to inWorkshop on Resource Allocation in Wireless.Networks (RAWNET), April2005.) also proposes consideration two-way link speed and predicts available bandwidth.But this method only is applicable to point coordination function (PCF; Point Coordination Function) medium access control (MAC; Medium Access Control); Distributed coordination function (DCF, Distributed Coordination Function) for extensive use in the WLAN product is also inapplicable.
Compare with maximum RSSI method, more than these methods considered that load, the direction of motion, transmitted in both directions etc. are more multifactor, under some scene, better system performance can be provided.But these prior aries above-mentioned all do not have to consider because the influence that node distributes and brings.In a sub-district, in the down link direction, an access point can listen to all wireless terminals in its coverage; But at uplink direction; Wireless terminal but can not listen to the existence of concealed terminal, when the node of concealed terminal sends packet simultaneously each other, can cause collision at the receiving node place; Therefore, concealed terminal can cause even more serious decreased performance than non-concealed terminal.
Fig. 3 shows the situation that throughput of system changes along with the number increase of wireless terminal under a BSS environment.As can be seen from Figure 3, when having concealed terminal, the increase of interstitial content can cause the obvious decline of uplink throughput.Therefore, need to consider the node distribution situation that the downlink information that utilizes AP to send is estimated the influence that brings owing to concealed terminal, thereby select the minimum access point of concealed terminal influence to carry out association/re-association.
Consider extensive use and the extensibility of framework formula WLAN, demand side is studied the selection problem when wireless terminal detects a plurality of AP under large-scale application environment to framework formula WLAN.Because IEEE802.11 is (referring to " ANSI/IEEE Std 802.11-1999Wireless LANMedium Access Control (MAC) and Physical Layer (PHY) Specifications "; 1999) many channels have been defined in the standard; Usually adopt non-overlapped channel (such as adopted channel 1 in the North America; 6; 11) avoid interference between the neighbor bss S, therefore suppose also that here the detected a plurality of BSS of wireless terminal work in different non-overlapped channels, promptly do not exist interference among adjacent cells yet.
Summary of the invention
In view of the above problems; The purpose of this invention is to provide a kind of access point (AP that in WLAN, selects; Access Point) method and apparatus can be estimated when inserting this AP because the influence that concealed terminal brings through wireless terminal difference measured channel busy extent on available channel; Thereby reduce the collision of upstream packet, improve the overall performance of WLAN.
According to an aspect of the present invention, a kind of method of in wireless network, selecting access point is provided, comprise step: a. wireless terminal is carried out scan channel to the channel in the network, receives the channel information that sends from access point, and from this information, takes out channel utilization u
kB. confirm the supported maximum data transfer rate v of current channel according to the channel information that receives
kC. add up the channel occupancy ratio r in trace interval
k, according to said channel utilization u
k, said maximum data transfer rate v
k, and said channel occupancy ratio r
kCalculate concealed terminal factor of influence f
kAll channels that d. can insert wireless terminal are carried out above-mentioned steps a to step c, and the concealed terminal factor of influence f that selects and calculated
kMiddle minimum is not the pairing access point AP of infinitely-great value, and adds the basic service set at selected access point place.
According to another aspect of the present invention; A kind of method of in wireless network, selecting access point is provided; Comprise step: the access point of a. wireless terminal in network sends probe requests thereby and divides into groups, and receives the response detected grouping that access point is beamed back, and from this information, takes out channel utilization u
kB. confirm the supported maximum data transfer rate v of current channel according to the channel information that receives
kC. add up the channel occupancy ratio r in trace interval
k, according to said channel utilization u
k, said maximum data transfer rate v
k, and said channel occupancy ratio r
kCalculate concealed terminal factor of influence f
kAll channels that d. can insert wireless terminal are carried out above-mentioned steps a to step c, and the concealed terminal factor of influence f that selects and calculated
kMiddle minimum is not the pairing access point AP of infinitely-great value, and adds the basic service set at selected access point place.
According to a further aspect of the invention, a kind of device of in wireless network, selecting access point is provided, comprises: channel scanning device, be used for the channel of network is carried out scan channel, receive the channel information that sends from access point; Judgment device is used for taking out channel utilization u from the information that channel scanning device receives
k, and confirm the supported maximum data transfer rate v of current channel according to the channel information that receives
kCalculate storage device, be used to store the channel utilization u that judgment device obtains
k, maximum data transfer rate v
k, and the channel occupancy ratio r of statistics in trace interval
kWith according to said channel utilization u
k, said maximum data transfer rate v
k, and said channel occupancy ratio r
kCalculate concealed terminal factor of influence f
kThe access point choice device is used for according to calculating the f of storage device to each channel calculation
kSelect access point; Transmission/receiving system is used for changing the channel of access according to the result that the access point choice device is selected, and on wave point, sends and receives information.
According to a further aspect of the invention, a kind of method of in wireless network, selecting access point is provided, comprises step: the information that in wireless network, receives the indicating channel behaviour in service; From the information that receives, obtain channel utilization u
k, and confirm supported maximum data transfer rate v
kAdd up the channel occupancy ratio r that this wireless terminal listens in sweep time during sweep time more than or equal to minimum
kCalculate f according to above value
k, and the f that selects and calculated
kMiddle minimum is not the infinitely-great pairing access point AP of value, and adds the basic service set at selected access point place.
According to the present invention, because based on existing WLAN standard IEEE802.11 agreement, and need not change the existing frame format of IEEE802.11e, therefore be easy to realize and have backwards compatibility preferably.
Description of drawings
Through below in conjunction with description of drawings the preferred embodiments of the present invention, will make above-mentioned and other purpose of the present invention, feature and advantage clearer, wherein:
Fig. 1 is the expression wireless terminal is selected access point in WLAN a sketch map;
Fig. 2 a and 2b are the sketch mapes of the wireless terminal process related with access point foundation in the explanation WLAN;
Fig. 3 explains schematically that under the BSS environment throughput of system is along with the quantity of wireless terminal increases and the situation of change;
Fig. 4 shows the sketch map of field relevant with channel utilization in the frame format according to the beacon of embodiment of the invention use and response detected grouping;
Fig. 5 shows the flow chart of in WLAN, selecting the process of WAP according to the embodiment of the invention;
Fig. 6 is the device of WAP is selected in expression in WLAN according to the embodiment of the invention a configuration block diagram;
Fig. 7 is the instance that the sequential chart of a kind of scan channel pattern of when selecting access point, carrying out according to the present invention is described;
Fig. 8 is another instance that the sequential chart of a kind of scan channel pattern of when selecting access point, carrying out according to the present invention is described; With
Fig. 9 is the instance that the sequential chart of the another kind of scan channel pattern of when selecting access point, carrying out according to the present invention is described.
Embodiment
With reference to the accompanying drawings embodiments of the invention are elaborated, in the description process, having omitted is unnecessary details and function for the present invention, obscures to prevent understanding of the present invention caused.
According to the present invention, the minimum sub-district of influence that the wireless terminal access is caused by concealed terminal.Method of the present invention comprises initial association and re-associates two parts.Initial association is meant when wireless terminal inserts WLAN at first and adopts above-mentioned passive or active scan mode to select an access point.As time goes on, the node in the network is distributed in continuous variation.Therefore wireless terminal need upgrade its access point to accomplish further optimization.If access point is based on the IEEE802.11 agreement, then need, the beacon of down link and response detected add the message segment of indicating channel utilance in dividing into groups; If access point is supported the IEEE802.11e agreement, then need not change beacon and response detected and divide into groups.
Fig. 4 shows the sketch map based on the quality of service basic service set load element (QBSS Load Element) in the frame format of the beacon of 802.11e standard definition and response detected grouping.The content that shown in Figure 4 is is wherein comprised in the ability information (capability information).Containing element id field in the current form, length (length) field, the number of standing (station count) field, channel utilization (channel utilization) and available access capacity field (available admissioncapacity) field.Wherein channel utilization is exactly the channel utilization u that need from the channel information of access point, obtain among the present invention
kTherefore, method of the present invention need not increase new territory or change frame format in the IEEE802.11e system.On the other hand, if this access point is the access point of traditional I EEE802.11, need in the reserved resource in its beacon and the response detected grouping, add channel usage (channel utilization) information of indicating channel utilance so.Be noted that to the invention is not restricted to this, also can adopt similar method to come the indicating channel utilance.
Wireless terminal can extract the information of indication channel utilization in beacon or the response detected grouping through the mode of drive sweep or active scan channel.
Describe the process that wireless terminal is selected access point in detail below in conjunction with Fig. 5.Fig. 5 shows the flow chart of in WLAN, selecting the process of WAP according to the embodiment of the invention.At first, at step S501, when wireless terminal got in the coverage of WLAN, this wireless terminal carried out parameter initialization and scanning channel successively, and wherein k representes the channel designator of current preparation scanning, u
kBe the channel utilization of this channel, the available channel sum that N supports for this wireless terminal.When initialization, can the channel designator k of current scanning be set at 1, u
kBe set at and bear 1, also do not receive the information of relevant channel utilization with the expression wireless terminal.At step S502, judge whether the channel quantity that has scanned has surpassed the available channel sum that this wireless terminal is supported.When the channel quantity that has scanned does not surpass the available channel sum, (being " denying " among the step S502); Flow process proceeds to step S503 and carries out scan channel; This step comprises drive sweep and active scan dual mode (with reference to figure 2): if drive sweep, then this wireless terminal is intercepted this channel and whether is received beacon packet to detect; If active scan, wireless terminal sends probe requests thereby grouping (ProbeRequest) and the response detected that awaits a response grouping after listening to channel idle so.After this, in step 504, judge whether that success receives beacon packet or the response detected grouping from AP.When successfully receiving when dividing into groups from the beacon packet of AP or response detected, at step S505, from ability information (capabilityinformation) element of these groupings, extract the information of channel utilization field, write down or be updated to u
kNext, at step S506, estimate the supported the maximum data transmission rate of this wireless terminal v
kAs an example, can estimate the supported the maximum data transmission rate of this wireless terminal v according to the energy or the reception carrier Signal Interference and Noise Ratio (SINR) of beacon that receives or response detected grouping
k, and judge whether reach minimum sweep time of T current sweep time at step S507
MinIf flow process proceeds to step S508, the channel occupancy ratio that statistics listened in the time of this channel of scanning is recorded as r
k, and can access degree value, i.e. concealed terminal factor of influence f according to following formula (1) estimation at step S509
k
f
k＝max(0，L
data/v
k*(u
k-r
k)) (1)
L wherein
DataIt is the average length of the packet that is ready for sending of this wireless terminal.After this,, the value of k is added 1, and return step S502 to prepare the next channel of scanning at step S510.
In the formula that in step S509, calculates (1), u
kCan reflect the load situation in the current area, the occupied ratio of channel just, r
kRepresent the node on every side that this wireless terminal can listen to, promptly non-concealed nodes, the time of busy channel.Therefore, (u
k-r
k) in fact be exactly that concealed terminal produces and the present unheard channel occupancy situation of this wireless terminal.Can predict the situation of concealed terminal through this difference.In addition, in transmission course, the transmission time of packet to be sent also can impact transmission.Transmission time is long more, and the probability that collides from the grouping generation of concealed terminal will be big more, and the influence that receives concealed terminal maybe be also just big more.Therefore with length and supported the maximum data transmission rate v of data to be sent
kRatio " the L of (by received energy or SINR decision)
Data/ v
k", in the transmission time of packet just, assess the influence that concealed terminal brings.Wireless terminal is near more from AP, and signal level that wireless terminal receives or carrier-in-interference noise ratio (SINR) are big more, the message transmission rate v that this wireless terminal is supported
kJust big more, " L
Data/ v
k" just more little; Equally, the length that outgoing data divides into groups is short more, its " L
Data/ v
k" also more little, to insert the possibility of this access point just big more for wireless terminal like this.
In addition, in step S507, if current sweep time is less than minimum T sweep time
Min, then turn back to step S503 and continue this channel of scanning.Be noted that minimum T sweep time
MinSetting depend on situation such as wireless terminal number in transmission rate and the current BSS of beacon period length, data packet length, packet, service distribution, its set point should satisfy can obtain the comparatively stable status transmission of channel in this sweep time.T
MinBig more, the statistics of channel seizure ratio is just accurate more, but the increase that can bring access delay; T
MinMore little, the error of statistics is just big more, but the time reduction of postponing a meeting or conference that inserts.In application, can set suitable value through emulation, environment or specific requirement.
Get back to step S504; If successfully receiving beacon or response detected in channel scan procedure, wireless terminal do not divide into groups; This comprises and receives data but fail reception; And not receiving any data in the time at the thresholding that sends after probe requests thereby is divided into groups, flow process then forwards step S511 to, detects u
kWhether more than or equal to zero, once received beacon in this terminal is during this scan channel or response detected is divided into groups if then show.At this moment, flow process forwards step S507 to, reaches minimum T sweep time in sweep time
MinThe time calculating channel occupation proportion.If step S511 judged result is " denying ", i.e. u
kLess than zero, show that this wireless terminal do not receive during this scan channel that beacon or response detected divided into groups.At this moment, flow process gets into step S512, judges whether to reach the maximum scan time T
MaxIf do not reach the maximum scan time yet, flow process turns back to step S503, continues k channel of scanning, under the drive sweep mode, continues to intercept, and is next according to the grouping of basic MAC access procedure repeating transmission probe requests thereby in the active scan mode, repeats said process.Reached the maximum scan time T sweep time if judge at step S512
Max, then in step S513, set f
kBe infinity, show that this channel is unavailable.After this, flow process proceeds to step S510, and the value of k is added 1, and returns step S502 to prepare the next channel of scanning.
When wireless terminal has scanned all wireless channels, (be " being " among the step S502), flow process proceeds to step S514, selects f
kValue is minimum and be the association with it of infinitely-great access point, and adds this basic service set.
Fig. 6 is the device of WAP is selected in expression in WLAN according to the embodiment of the invention a configuration block diagram.Describe the configuration embodiment that the present invention selects the device of WAP below in detail.
For fear of the present invention and prior art are obscured, in the description process, having omitted is unnecessary details and function for the present invention, and only describes the part relevant with the present invention.It will be understood by those skilled in the art that
The device of said selection access point is included in the wireless terminal.Device according to selection access point of the present invention comprises transmission/receiving system 61, channel scanning device 62, access point choice device 63, judgment device 64 and calculating storage device 65.Transmission/receiving system 61 changes channel according to the result of channel scanning device 62 and 63 outputs of access point choice device, on wave point, sends and receives information.The state of channel scanning device 62 scanning channels is also delivered to judgment device 64 with scanning result.In addition, when channel scanning device 62 indication begins to scan a new channel, carry out the initialization of parameter to calculating storage device 65, and change the channel that transmissions/receiving system 61 is operated.Judgment device 64 receives from the result of channel scanning device 62 and makes judgement.When the thresholding when channel scanning device 62 receives non-noise information or sending the probe requests thereby grouping in scanning process after did not receive any data in the time, judgment device 64 judged whether channel scanning device 62 has correctly received beacon or response detected grouping.If beacon or response detected grouping are then sent into calculating storage device 65 to this grouping and are handled.Otherwise judgment device 64 further detects the u on this channel in the current calculating storage device 65
kWhether be zero.If then indicating channel scanning means 62 continues scanning channel, till judgment device 64 judges that sweep time is more than or equal to minimum sweep time.At this moment, judgment device 64 notices are calculated storage device 65 and are calculated above-mentioned relevant information.If u
kNon-vanishing, then continue to judge whether reached the maximum scan time sweep time.Send a notice in the condition that reaches the maximum scan time and to calculate storage device 65 channel occupancy ratio f
kBe set at infinity.Otherwise indicating channel scanning means 62 continues scanning channel, under the drive sweep mode, continues to intercept, and is next according to the grouping of basic MAC access procedure repeating transmission probe requests thereby in the active scan mode, repeats said process.In addition, judgment device 64 also receives calculates the information that storage device 65 calculates, and judges whether to have scanned all channels.If then indicating channel scanning means 62 scans next channel.Otherwise indication access point choice device 63 is according to calculating the f that storage device 65 is calculated
kSelect access point.
Indicate when receiving that successfully beacon packet or response detected are divided into groups when judgment device 64, from these divide into groups, extract channel utilization u
kAnd confirm maximum supported message transmission rate v according to the energy that receives these groupings
k, and these results are sent into calculate storage device 65.When the 64 beacon scanning times of judgment device more than or equal to T
MinThe time, calculate storage device 65 calculating channel occupation proportion r
k, and according to existing u
k, v
kCalculate f
k=max (0, L
Data/ v
k* (u
k-r
k)).When the 64 beacon scanning times of judgment device more than or equal to T
MaxThe time, calculate storage device 65 and set f
k=inf (infinity).When judgment device 64 indications had scanned all channels, indication access point choice device 63 was selected access point.Access point choice device 63 is selected f according to calculating the information that storage device 65 provides
kValue is minimum and be that infinitely-great access point is prepared to insert, and notifies transmission/receiving system 61 to be operated on the channel of this access point work.
After network access by wireless terminal, the state in can be Network Based changes working channel, utilizes said process to reselect access point, promptly carries out re-associates.
According to the present invention, during the request of or re-associates relevant, scan each channel successively when certain wireless terminal,, the beacon that receives or response detected obtain channel utilization information u from dividing into groups
k, and confirm supported maximum data transfer rate v according to grouping energy of receiving or SINR
k, add up the channel occupancy ratio r that this wireless terminal listens to during sweep time more than or equal to minimum in sweep time
k, calculate f according to above value
k=max (0, L
Data/ v
k* (u
k-r
k)),, all scan channels select to have minimum f after finishing
kAnd f
kDo not insert for infinitely-great channel.
Fig. 7 be explanation according to an instance of the present invention, the sequential chart during with passive scan channel model selection access point.
At this, be that example describes with two access points, be appreciated that method of the present invention can use any amount of access point, and do not have specific limited.Can suppose that access point AP1 and AP2 work in non-overlapped channel CH respectively
1And CH
2On, and with fixing beacon interval period property ground transmission beacon packet Beacon.According to the IEEE802.11 agreement, when access point at target beacon delivery time (TBTT, Target Beacon Transmission Time) when detecting channel busy, send beacon packet after should being deferred to channel idle.Therefore, the time interval of access point AP1 and AP2 transmission beacon packet Beacon is fluctuating at the fixed beacon interval.
As shown in Figure 7, at T
1Constantly, wireless terminal MT gets into wlan network because of it, or reason such as service quality variation produces the request that access point is selected or reselected.At this moment, wireless terminal MT utilizes 62 pairs of parameters of channel scanning device to carry out initialization and begin to scan CH
1At T2 constantly, wireless terminal MT judges that through judgment device 64 channel scanning device 62 successfully receives the beacon packet from AP1, from this divides into groups, takes out channel utilization u
1, and offer and calculate storage device 65 and be kept at wherein.Meanwhile, judgment device 64 also decides supported maximum data transfer rate v according to the energy of the beacon packet that receives
1And be kept in the calculating storage device 65.Accomplish above-mentioned information extraction and confirming supported maximum data transfer rate v
1After, whether judgment device 64 detects sweep time more than or equal to minimum T sweep time
Min, as shown in Figure 7, because (T
2-T
1)＞T
MinSo judgment device 64 notices are calculated storage device 65 statistics at T
1To T
2The time interval in channel occupancy ratio r
1, and according to the channel occupancy ratio r that adds up
1Calculate f
1=max (0, L
Data/ v
1* (u
1-r
1)).After this, judgment device 64 is detecting when not scanned all channels, and notification channel scanning means 62 begins to scan next channel CH
2
At T
3Constantly, wireless terminal MT judges the beacon packet that successfully receives from AP2 through judgment device 64, therefrom takes out channel utilization u
2And it is kept at calculates in the storage device, the energy according to the beacon packet that receives determines supported maximum data transfer rate v simultaneously
2And it is kept at calculates in the storage device 65.After this, whether judgment device detects sweep time more than or equal to minimum T sweep time
MinAs shown in Figure 7, because (T
3-T
2)＜T
MinSo judgment device 64 continues scanning channel up to T
4Constantly, satisfy (T
4-T
2)=T
Min.
At T
4Constantly, wireless terminal MT calculates storage device 65 statistics at T through judgment device 64 notices
2To T
4The time interval in channel occupancy ratio r
2, and calculate f
2=max (0, L
Data/ v
2* (u
2-r
2)).After this, judgment device 64 detects and has scanned all channels, so notice access point choice device 63 is according to the result of calculation selection f that calculates storage device 65
1, f
2The middle minimum pairing access point AP of value.Here, if f
1And f
2Equate, then at random or according to other existing AP systems of selection, such as maximum RSSI, minimum load etc. are selected an AP.
At T
4After access point was selected to finish constantly, wireless terminal MT initiates association or re-associates is set up request (Association Request/Reassociation Request).Receiving that successfully association or re-associates acknowledgment packet (Association Response/Reassociation Response) back adds the basic service set at selecteed access point place.
Fig. 8 be explanation according to the present invention the sequential chart with another instance of passive scan channel model selection access point.
With example class shown in Figure 7 seemingly, at T
1Constantly, wireless terminal MT utilizes channel scanning device 62 to carry out parameter initialization and begins to scan CH
1At T
2Constantly, wireless terminal MT receives data through channel scanning device 62, but judgment device 64 is judged the reception that fails of these data, then in the detection computations storage device 65 corresponding to the utilance u of current channel
kWhether greater than zero, owing to during scan channel, successfully do not received beacon packet, so u
kIt still is initial value-1.Next wireless terminal continues scanning channel, up to reaching the maximum scan time T
MaxAt T
3Constantly, judgment means 64 indications of wireless terminal MT reach the maximum scan time T
MaxSo notice is calculated storage device 65 and is set f
1Be infinity.After this, judgment device 64 detects also has the not channel of scanning, so notification channel scanning means 62 begins to scan next channel CH
2After this T
3To T
5T in the operation in the moment and the instance shown in Figure 7
2To T
4Operation constantly is identical, omits the explanation to it at this.Next, at T
5Constantly, to channel CH2, wireless terminal MT calculates storage device 65 statistics at T through judgment device 64 notices
3To T
5The time interval in channel occupancy ratio r
2, and calculate f
2=max (0, L
Data/ v
2* (u
2-r
2)).After this, judgment device 64 detects and has scanned all channels, so notice access point choice device 63 is according to the result of calculation selection f that calculates storage device 65
1, f
2The middle minimum corresponding access point AP of value.Because f
1Be infinity, therefore can only select AP2.At this moment, wireless terminal MT initiates association or re-associates foundation request (AssociationRequest/Reassociation Request).Receiving that successfully association or re-associates acknowledgment packet (Association Response/Reassociation Response) back adds the basic service set at selecteed access point place.
Fig. 9 explains according to a further embodiment of the invention, the sequential chart when selecting access point with the active channel scan pattern.
At T
1Constantly, wireless terminal MT is because of getting into wlan network, or reason such as service quality variation produces the request that access point is selected or reselected.At this moment, wireless terminal MT utilizes channel scanning device 62 to carry out parameter initialization, and is detecting CH
1Under the idle situation according to media access control protocol at CH
1Last transmission probe requests thereby grouping (P_Req, Probe Request).At T
2Constantly, access point AP1 successfully receives from the probe requests thereby of wireless terminal MT and divides into groups, and responds the grouping that receives, and sends response detected grouping (P_Res, Probe Response).The utilance information u that comprises current channel during response detected is divided into groups
1At T
3Constantly, wireless terminal MT detects success through judgment device 64 and receives the response detected grouping from MT, and responds affirmative acknowledgement grouping (ACK), utilizes judgment device 64 to take out channel utilization u simultaneously
1And it is kept at calculates in the storage device 65.In addition, judgment device 64 decides supported maximum data transfer rate v according to the energy of the response detected grouping that receives
1And it is kept at calculates in the storage device 65.At T
4Constantly, wireless terminal MT sends ACK and divides into groups to finish, and judges that through judgment device 64 whether sweep time is more than or equal to minimum T sweep time
Min, because (T
4-T
1)＞T
MinSo the judgment device notice is calculated storage device 65 statistics at T
1To T
4The time interval in channel occupancy ratio r
1, and calculate f
1=max (0, L
Data/ v
1* (u
1-r
1)) value.After this, judgment device 64 is detecting when not scanned all channels, and notification channel scanning means 62 begins to scan next channel CH
2
At T5 constantly, wireless terminal MT detects CH
2Free time is at channel CH
2The transmission probe requests thereby is divided into groups.After this response detected is divided into groups, transmission and T that affirmative acknowledgement is divided into groups
1To T
4Said process constantly is identical, omits the description to it at this.After this, at T
6Constantly, wireless terminal MT sends it back and answers affirmative acknowledgement ACK to divide into groups to finish, and judges sweep time less than minimum T sweep time through judgment device 64
Min, i.e. (T
6-T
4)＜T
MinSo judgment device 64 notification channel scanning means 62 continue scanning channel, up to T
7Constantly, satisfy (T
7-T
4)=T
MinAt T
7Constantly, wireless terminal MT calculates storage device 65 statistics at T through judgment device 64 notices
4To T
7Channel occupancy ratio r in the time interval
2, and calculate f
2=max (0, L
Data/ v
2* (u
2-r
2)) value.After this, judgment device 64 detects and has scanned all channels, so notice access point choice device 63 is according to the result of calculation selection f that calculates storage device 65
1, f
2The middle minimum corresponding access point AP of value.Here, if f
1And f
2Equate, then at random or according to other existing AP systems of selection, such as maximum RSSI, minimum load etc. are selected an AP.At T
7After access point was selected to finish constantly, wireless terminal MT initiates association or re-associates is set up request (Association Request/ReassociationRequest), added the basic service set at selecteed access point AP place.
According to the present invention; Wireless terminal obtains it through scan channel and intercepts the channel usage degree r that scope is brought with interior non-concealed terminal node; According to entrained channel utilization information u in beacon of receiving or the response detected grouping, can estimate the channel occupancy ratio (u-r) that concealed terminal brought in this basic service set simultaneously; Because the time of data packet transmission is depended in the collision that concealed terminal brings, therefore can use f again
k=max (0, L
Data/ v
k* (u
k-r
k)) estimate when this wireless terminal is worked on k channel to have improved the total throughout of system because the influence that concealed terminal brings inserts thereby select to receive concealed terminal to influence minimum access point.The present invention is based on prior protocols, adopt the frame format that defines in the existing communication agreement fully, realize simply having good using value.
So far invention has been described in conjunction with the preferred embodiments.Should be appreciated that those skilled in the art can carry out various other change, replacement and interpolations under the situation that does not break away from the spirit and scope of the present invention.Therefore, scope of the present invention is not limited to above-mentioned specific embodiment, and should be limited accompanying claims.
Claims (27)
1. method of in wireless network, selecting access point comprises step:
A. wireless terminal is carried out scan channel to the channel in the network, receives the channel information that sends from access point, and from this information, takes out channel utilization u
k
B. confirm the supported maximum data transfer rate v of current channel according to the channel information that receives
k
C. add up the channel occupancy ratio r in trace interval
k, according to said channel utilization u
k, said maximum data transfer rate v
k, and said channel occupancy ratio r
kCalculate concealed terminal factor of influence f
k
All channels that d. can insert wireless terminal are carried out above-mentioned steps a to step c, and the concealed terminal factor of influence f that selects and calculated
kMiddle minimum is not the pairing access point AP of infinitely-great value, and adds the basic service set at selected access point place,
Wherein, calculate f according to following expression
k:
f
k＝max(0，L
data/v
k*(u
k-r
k))
L wherein
DataBe the average length of the packet that is ready for sending of this wireless terminal, k representes the channel designator of current scanning.
2. method according to claim 1, wherein wireless terminal decides supported maximum data transfer rate v according to the energy information that comprises in the channel information that receives
k
3. method according to claim 1, wherein said step c further comprises and detects sweep time whether more than or equal to minimum sweep time of T
MinIf then continue scanning current channel less than minimum sweep time sweep time, include channel utilization u from access point until receiving
kThe step of channel information.
4. method according to claim 1 further comprises Initial Channel Assignment utilance u
kStep with the channel designator that is scanned.
5. method according to claim 1 comprises that further in wireless network, having at least two has identical f
kAccess point the time, from having identical f
kAccess point in select the step of an access point at random.
6. method according to claim 1 further is included in calculating channel occupation proportion r under the condition that has reached minimum sweep time
kAnd f
kStep.
7. method according to claim 1 further is included in wireless terminal and fails when receiving channel information, continues scanning channel, up to reaching the maximum scan time T
Max, and reaching the maximum scan time T
MaxThe time, set f
kBe infinitely-great step.
8. method according to claim 1 further comprises when wireless terminal does not listen to any beacon packet, is reaching maximum scan during the time, sets f
kBe infinitely-great step.
9. method according to claim 8 comprises that further working as wireless terminal does not listen under the situation of any beacon packet, if do not reach the maximum scan time yet, then continues the current channel of scanning.
10. method according to claim 1 comprises that further working as wireless terminal does not listen under the situation of any beacon packet, when detecting channel utilization u
kMore than or equal to zero the time, then reach minimum sweep time of T in sweep time
MinThe time calculating channel occupation proportion.
11. a method of in wireless network, selecting access point comprises step:
A. wireless terminal divides into groups through the transmission of the access point in network probe requests thereby, and receives the response detected grouping that access point is beamed back, and comes the channel in the network is carried out scan channel, and from this response detected grouping, takes out channel utilization u
k
B. confirm the supported maximum data transfer rate v of current channel according to the channel information that receives
k
C. add up the channel occupancy ratio r in trace interval
k, according to said channel utilization u
k, said maximum data transfer rate v
k, and said channel occupancy ratio r
kCalculate concealed terminal factor of influence f
k
All channels that d. can insert wireless terminal are carried out above-mentioned steps a to step c, and the concealed terminal factor of influence f that selects and calculated
kMiddle minimum is not the pairing access point AP of infinitely-great value, and adds the basic service set at selected access point place,
Wherein, calculate f according to following expression
k:
f
k＝max(0，L
data/v
k*(u
k-r
k))
L wherein
DataBe the average length of the packet that is ready for sending of this wireless terminal, k representes channel designator.
12. method according to claim 11, wherein wireless terminal decides supported maximum data transfer rate v according to the energy information that comprises in the channel information that receives
k
13. method according to claim 11, wherein said step c further comprises and detects sweep time whether more than or equal to minimum sweep time of T
MinIf then continue scanning current channel less than minimum sweep time sweep time, include channel utilization u from access point until receiving
kThe step of channel information.
14. method according to claim 11 further comprises Initial Channel Assignment utilance u
kStep with the channel designator that is scanned.
15. method according to claim 11 comprises that further in wireless network, having at least two has identical f
kAccess point the time, from having identical f
kAccess point in select the step of an access point at random.
16. method according to claim 11 further is included in calculating channel occupation proportion r under the condition that has reached minimum sweep time
kAnd f
kStep.
17. method according to claim 11 further is included in wireless terminal and fails when receiving channel information, continues scanning channel, up to reaching the maximum scan time T
Max, and reaching the maximum scan time T
MaxThe time, set f
kBe infinitely-great step.
18. method according to claim 11 when comprising that further after wireless terminal is sending the probe requests thereby grouping, not receiving response detected divides into groups, is reaching maximum scan during the time, sets f
kBe infinitely-great step.
19. method according to claim 18 further comprises when wireless terminal is sending not receiving under the situation of response detected grouping after probe requests thereby is divided into groups, if do not reach the maximum scan time yet, then retransmits probe requests thereby and divides into groups.
20. method according to claim 11 further comprises when wireless terminal is sending not receiving under the situation of response detected grouping, when detecting channel utilization u after probe requests thereby is divided into groups
kMore than or equal to zero the time, then reach minimum sweep time of T in sweep time
MinThe time calculating channel occupation proportion.
21. a device of in wireless network, selecting access point comprises:
Channel scanning device is used for the channel of network is carried out scan channel, receives the channel information that sends from access point;
Judgment device is used for taking out channel utilization u from the information that channel scanning device receives
k, and confirm the supported maximum data transfer rate v of current channel according to the channel information that receives
k
Calculate storage device, be used to store the channel utilization u that judgment device obtains
k, maximum data transfer rate v
k, and the channel occupancy ratio r of statistics in trace interval
kWith according to said channel utilization u
k, said maximum data transfer rate v
k, and said channel occupancy ratio r
kCalculate concealed terminal factor of influence f
k
The access point choice device is used for according to calculating the f of storage device to each channel calculation
kSelect access point;
Transmission/receiving system is used for changing the channel of access based on the result that the access point selecting arrangement is selected, and on wave point, sends and receives information,
Wherein said calculating storage device calculates f according to following expression
k:
f
k＝max(0，L
data/v
k*(u
k-r
k))
L wherein
DataBe the average length of the packet that is ready for sending of this wireless terminal, k representes channel designator.
22. when device according to claim 21, wherein said channel scanning device begin to scan a new channel in indication, the parameter of calculating memory device stores is carried out initialization.
23. whether device according to claim 21, wherein said judgment device detect sweep time more than or equal to minimum T sweep time
MinIf then continue scanning current channel less than minimum sweep time sweep time.
24. device according to claim 21 wherein fails when receiving channel information in said judgment device, continues scanning channel, up to reaching the maximum scan time T
Max, and reaching the maximum scan time T
MaxThe time, set f by said calculating storage device
kBe infinity.
25. device according to claim 21 when wherein after said judgment device does not listen to any beacon packet or sending the probe requests thereby grouping, not receiving the response detected grouping, is reaching maximum scan during the time, sets f by said calculating storage device
kBe infinity.
26. a wireless terminal is selected the method for access point in wireless network, comprise step:
In wireless network, receive the information of indicating channel behaviour in service;
From the information that receives, obtain channel utilization u
k, and confirm supported maximum data transfer rate v
k
Add up the channel occupancy ratio r that this wireless terminal listens in sweep time during sweep time more than or equal to minimum
k
Calculate f according to above value
k, and to all channels execution above-mentioned steps that this wireless terminal can insert, select and the f that is calculated
kMiddle minimum is not the pairing access point AP of infinitely-great value, and adds the basic service set at selected access point place,
Wherein, calculate f according to following expression
k:
f
k＝max(0，L
data/v
k*(u
k-r
k))
L wherein
DataBe the average length of the packet that is ready for sending of this wireless terminal, k representes channel designator.
27. method according to claim 26 wherein reaching the maximum scan time and failing when receiving channel information, will be set f
kBe infinity.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200610110741 CN101123802B (en) | 2006-08-08 | 2006-08-08 | Method and device for selecting access point in wireless LAN |
| JP2007206469A JP5118918B2 (en) | 2006-08-08 | 2007-08-08 | Method and apparatus for selecting an access point in a wireless local network |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200610110741 CN101123802B (en) | 2006-08-08 | 2006-08-08 | Method and device for selecting access point in wireless LAN |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101123802A CN101123802A (en) | 2008-02-13 |
| CN101123802B true CN101123802B (en) | 2012-01-11 |
Family
ID=39085925
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200610110741 Active CN101123802B (en) | 2006-08-08 | 2006-08-08 | Method and device for selecting access point in wireless LAN |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP5118918B2 (en) |
| CN (1) | CN101123802B (en) |
Families Citing this family (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101667871B (en) * | 2008-09-04 | 2013-03-06 | 上海无线通信研究中心 | Channel pre-allocation method for accelerating random access of CPE to CR networks |
| US8547942B2 (en) | 2008-10-17 | 2013-10-01 | Sumitomo Electric Industries, Ltd. | Transmitter station with detectable function for radio condition |
| JP5395615B2 (en) | 2009-10-27 | 2014-01-22 | キヤノン株式会社 | Wireless communication apparatus, control method and program for wireless communication apparatus |
| US8953543B2 (en) | 2010-06-09 | 2015-02-10 | Panasonic Corporation | Communication terminal, control device, communication method, control method, program, and integrated circuit |
| CN104796895A (en) * | 2011-12-21 | 2015-07-22 | 上海云联计算机系统有限公司 | Method, system, server and mobile terminal capable of quickly accessing into public wireless local area network |
| CN103200646B (en) | 2012-01-09 | 2016-03-30 | 华为技术有限公司 | A kind of method of terminal and terminal active scan |
| CN105376837B (en) * | 2012-01-09 | 2019-02-19 | 华为技术有限公司 | A kind of method of terminal and terminal active scan |
| CN103249118A (en) * | 2012-02-10 | 2013-08-14 | 联想(北京)有限公司 | Wireless access point selection method and electronic terminals |
| CN102905343B (en) * | 2012-10-10 | 2015-09-16 | 福建星网锐捷网络有限公司 | Radio switch-in method and Radio Access Controller |
| GB2507492B (en) | 2012-10-30 | 2014-11-19 | Toshiba Res Europ Ltd | Wireless communication methods and apparatus |
| JP5962452B2 (en) | 2012-11-19 | 2016-08-03 | 富士通株式会社 | Wireless communication system, wireless communication method, and transmission terminal |
| JP5954130B2 (en) | 2012-11-19 | 2016-07-20 | 富士通株式会社 | Wireless communication system, wireless communication method, transmitting terminal, and receiving terminal |
| CN103546911B (en) * | 2013-11-12 | 2016-04-20 | 上海交通大学 | The method of wireless access point selection optimum channel |
| JP6053177B2 (en) * | 2013-12-09 | 2016-12-27 | 日本電信電話株式会社 | Heterogeneous network system and communication line selection method |
| KR102275025B1 (en) * | 2014-11-21 | 2021-07-08 | 삼성전자주식회사 | Method for providing wireless lan service and electronic device thereof |
| CN106535293B (en) * | 2015-09-09 | 2020-10-27 | 华为技术有限公司 | Active scanning processing method and related device and communication system |
| WO2017046159A1 (en) * | 2015-09-15 | 2017-03-23 | Philips Lighting Holding B.V. | Provisioning of a wireless device without keypad |
| CN108633030A (en) * | 2017-03-24 | 2018-10-09 | 中兴通讯股份有限公司 | Channel access method and device |
| JP6691888B2 (en) * | 2017-03-30 | 2020-05-13 | 日本電信電話株式会社 | Wireless communication system and wireless communication control method |
| US10966140B2 (en) * | 2019-06-17 | 2021-03-30 | Nanning Fugui Precision Industrial Co., Ltd. | Method for detecting and filtering out unauthorized wireless access point and device using the method |
| CN110996357B (en) * | 2019-12-09 | 2021-12-03 | 深圳市吉祥腾达科技有限公司 | Terminal distribution optimization method, system and storage medium under multiple access points |
| CN113114521B (en) * | 2021-02-24 | 2022-10-04 | 浙江大华技术股份有限公司 | Link quality judging method, network camera and readable storage medium |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1542405A2 (en) * | 2003-12-09 | 2005-06-15 | Agere System Inc. | Access point selection using channel correlation in a wireless communication system |
| CN1675954A (en) * | 2002-08-23 | 2005-09-28 | 皇家飞利浦电子股份有限公司 | Dynamic frequency selection in a WLAN |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7609648B2 (en) * | 2003-06-19 | 2009-10-27 | Ipr Licensing, Inc. | Antenna steering for an access point based upon control frames |
| KR20050017705A (en) * | 2003-08-07 | 2005-02-23 | 한국전자통신연구원 | Method for Association in Public Wireless LAN |
| JP2005244721A (en) * | 2004-02-27 | 2005-09-08 | Mitsubishi Electric Corp | Method for selecting wireless lan base station, and wireless lan terminal station |
-
2006
- 2006-08-08 CN CN 200610110741 patent/CN101123802B/en active Active
-
2007
- 2007-08-08 JP JP2007206469A patent/JP5118918B2/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1675954A (en) * | 2002-08-23 | 2005-09-28 | 皇家飞利浦电子股份有限公司 | Dynamic frequency selection in a WLAN |
| EP1542405A2 (en) * | 2003-12-09 | 2005-06-15 | Agere System Inc. | Access point selection using channel correlation in a wireless communication system |
Non-Patent Citations (2)
| Title |
|---|
| S. Vasudevan等.Facilitating Access Point Selection in IEEE 802.11 Wireless Networks.《Internet Measurement Conference 2005》.2005,第293-298页. * |
| T. Korakis等.Link Quality based Association Mechanism in IEEE.《1st worshop on Resource Allocation in Wireless Networks》.2005,全文. * |
Also Published As
| Publication number | Publication date |
|---|---|
| JP5118918B2 (en) | 2013-01-16 |
| JP2008042922A (en) | 2008-02-21 |
| CN101123802A (en) | 2008-02-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN101123802B (en) | Method and device for selecting access point in wireless LAN | |
| US8170546B2 (en) | Client device characterization of other client device transmissions and reporting of signal qualities to access point(s) | |
| CN105453686B (en) | Method and apparatus for accessing channel | |
| CN101136821B (en) | Device and method for controlling the transmission power of a basic service set in a wireless local area network | |
| US7907582B2 (en) | Method and apparatus for access point selection in wireless LAN | |
| Alawieh et al. | Improving spatial reuse in multihop wireless networks-a survey | |
| US7864742B2 (en) | Cell network using friendly relay communication exchanges | |
| US7720038B2 (en) | Cell network selectively applying proxy mode to minimize power | |
| US20040039817A1 (en) | Enhanced algorithm for initial AP selection and roaming | |
| US20080056201A1 (en) | Interference parameter reporting from client devices to access point for use in modifying wireless operations | |
| US9439136B2 (en) | Method and apparatus for scanning in wireless LAN | |
| US9609664B2 (en) | Layered channel access method and apparatus in wireless local area network system | |
| Zhu et al. | On improving the performance of IEEE 802.11 with relay-enabled PCF | |
| WO2010096029A1 (en) | Distributed channel selection method for wireless networks | |
| EP1943863B1 (en) | Communication network | |
| US9883535B2 (en) | Channel access method and apparatus therefor | |
| Oni et al. | Decentralized AP selection in large-scale wireless LANs considering multi-AP interference | |
| Lv et al. | SWIMMING: seamless and efficient WiFi-based internet access from moving vehicles | |
| Ma et al. | A QoS-based vertical handoff scheme for interworking of WLAN and WiMAX | |
| Du et al. | Access point selection strategy for large-scale wireless local area networks | |
| Wan et al. | A new ap-selection strategy for high density ieee802. 11 wlans | |
| CN107046730B (en) | Data transmission method and device | |
| Kobayashi et al. | Spatially divided channel scheme using sectored antennas for CSMA/CA" directional CSMA/CA" | |
| Kuboniwa et al. | High efficient network selection scheme using location information for heterogeneous wireless system | |
| Zhu et al. | Leveraging multi-AP diversity for transmission resilience in wireless networks: architecture and performance analysis |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant |